In the summer of 1953 the town of Sheffield, Pennsylvania is struck by a typhoid fever epidemic. Johnnie Marlowe and his friends anxiously await the arrival of a CDC epidemiologist who will investigate the cause. Suspicion has already involved a reclusive old man known for hoarding and his equally eccentric clairvoyant sister who has mysteriously disappeared. The medical detective arrives, and to the boys’ surprise, they discover that the epidemiologist is a young woman. With the boys’ help, and using the standard investigative tools, she considers the water supply, milk and food as the possible source of the epidemic. Townspeople, aroused by an outside agitator wishing to pin blame on the elderly couple for his gain, assemble in an angry mob. But, will the surprising source of the epidemic be revealed before the crowd torches the couple’s house?